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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

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TURNER, HAENKE AND HUBBARD GLACIERS                  95
pronounced medial moraine. Clear ice exceeded debris-laden ice in the south half of the glacier, while in the north half there were no medial moraines and the north lateral moraine was not wide.
The ice cliff is in general regular, reaching its maximum height within a quarter of a mile of the south side. In detail it is made up of innumerable points and recesses, the foremost cape being south of the middle of the glacier. Rapid movement, of undetermined rate, is indicated by severe crevassing and incessant iceberg discharge, even the d6bris-laden wing-tips being much broken in 1905.
Changes Between 1891 and 1906. Photographs taken in 1905 on Haenke Island from the exact site of Gilbert's 1899 picture, and from as near the site of Russell's 1891 picture as the growth of alder would permit its location, show the following changes, which have previously been announced.1
Between 1891 and 1905 Turner Glacier receded, the moraine-veneered tip, and the edge of the clear ice on the south, going back two to three hundred yards and the north edge an equal amount. The centre of the glacier receded a quarter of a mile, as shown by the truncation of the medial moraine. There were minor differences in the distribution of moraine on the ice.
Between 1899 and 1905 the middle of the glacier receded, showing that fully two-thirds of the recession of Turner Glacier between 1891 and 1905 took place between 1899 and 1905. But the north and south glacier tips advanced, both the clear and the debris-laden ice on the north side extending fully a quarter of a mile farther in 1905 than in 1899, while the south side advanced one or two hundred yards and was greatly broken clear up to the edge.
Therefore, as Gilbert showed, there was recession between 1891 and 1899; but there was net recession between 1891 and 1905 with advance of the middle between 1899 and 1901 and with advance and breaking on the edges and retreat in the center between 1901 and 1905.
This general recession is evidenced along the south margin of Turner Glacier where there was a low moraine in 1905 with no ice in it and no vegetation upon its surface. This was perhaps the moraine that the glacier margin touched at the time of Russell's 1891 picture. Just beyond this, and not far above the present glacier surface, the growth of good-sized alders, estimated to be not less than 20 years old, proved that the glacier had not recently been much higher than in 1905. No spruces had advanced within several miles of Turner Glacier.
Condition in 1906 and 1909. The only noticeable modification between 1905 and 1906 was a slight change in the position of the medial moraine, suggesting a minor advance in the central portion of the glacier. In 1909, however, notable change was seen. By comparing the 1906 and 1909 views of Turner Glacier from Osier Island, recession in the northern wing was indicated by the noticeable increase hi the area covered by moraine. A visit to the southern margin was made and photographic sites of 1905 and 1906 were re-occupied. Here it was found that the southern wing had receded sjightly (PI. XXXIX) and its crevassed condition had disappeared, being replaced by a moraine-covered, uncrevassed margin, and that the ice over the steep part of the glacier was
i Tarr, R. S. and Martin, Lawrence, Glaciers and Glaciation of Yakutat Bay, Alaska, Bull. Amer. Geog. Soc., Vol. XXXVm, 1906, p. 154; Tarr, R. S., the Yakutat Bay Region. Alaska, Professional Paper 64, U. S. Geol. Survey, 1909, pp. 40-41.